New telescope will scan the skies for asteroids on collision course with Earth

Around sunrise on Feb. 15, 2013, an extremely bright and otherworldly object was seen streaking through the skies over Russia before it exploded about 97,000 feet above the Earth’s surface. The resulting blast damaged thousands of buildings and injured almost 1,500 people in Chelyabinsk and the surrounding areas. While this sounds like the first scene of a science fiction movie, this invader wasn’t an alien spaceship attacking humanity, but a 20-meter-wide asteroid that had collided with the Earth.

What is worrisome is that no one had any idea this 20-meter asteroid existed until it entered the Earth’s atmosphere that morning.

As an astronomer, I study objects in the sky that change in brightness over short time scales — observations that I use to detect planets around other stars. A large part of my research is understanding how we can better design and run telescopes to monitor an ever-changing sky. That’s important because the same telescopes I’m using to explore other star systems are also being designed to help my colleagues discover objects in our own solar system, like asteroids on a collision course with with Earth.

Near-Earth objects

A meteor is any chunk of matter that enters the Earth’s atmosphere. Before the Chelyabinsk meteor met its demise on Earth, it was orbiting our sun as an asteroid. These rocky objects are normally thought to be restricted to the asteroid belt between Mars and Jupiter. However, there are many asteroids throughout the solar system. Some, like the Chelyabinsk meteor, are known as near-Earth objects (NEOs).

Searching for threats

The U.S. government is taking the threat of an asteroid collision seriously. In Section 321 of the NASA Authorization Act of 2005, Congress required NASA develop a program to search for NEOs. NASA was assigned the task of identifying 90 percent of all NEOs greater than 140 meters in diameter. Currently, they estimate that three-quarters of the 25,000 PHAs have yet to be found.

To reach this goal, an international team of of hundreds of scientists, including myself, is completing construction of the Large Synoptic Survey Telescope (LSST) in Chile, which will be an essential tool for alerting us of PHAs.

With significant funding from the U.S. National Science Foundation, LSST will search for PHAs during its 10-year mission by observing the same area of sky at hourly intervals searching for objects that have changed position. Anything that moves in just one hour has to be so close that it is within our solar system. Teams led by researchers at the University of Washington and JPL have both produced simulations showing that LSST on its own will be capable of finding around 65 percent of PHAs. If we combine LSST data with other astronomical surveys like Pan-STARRS and the Catalina Sky Survey, we think we can help reach that goal of discovering 90 percent of potentially hazardous asteroids.